The (ugly) workaround I'm using since years on this issue:

• type an 'x' and the end
• move the cursor left next to the 'x'
• press shift-enter a couple of times to get the blank lines needed
• edit those lines
• finally remove the trailing 'x'

I just ran into this bug while using VisualEditor and preformatted text. I consider this a severe issue in the preformatted editor, so I wonder if this could be raised and fixed.